Jennifer Flanagan, of Leominster, will resign from her state senate seat to serve on the commission

BOSTON — A Democratic state senator who opposed the ballot question that legalized recreational marijuana was named Wednesday by Republican Gov. Charlie Baker to the regulatory board that will oversee the cannabis industry in Massachusetts.

Sen. Jennifer Flanagan, of Leominster, is the first appointee to the five-member Cannabis Control Commission. She will serve as an associate commissioner beginning on Sept. 1 after resigning from her Senate seat at the end of the month.

The governor, in a statement, touted Flanagan’s experience in the Legislature on issues involving substance abuse prevention, treatment and recovery as invaluable to the state’s goal of “effective, responsible and safe implementation of the adult use of marijuana.”

Flanagan played a key role in crafting a 2016 state law that offered several new approaches to stemming the deadly opioid addiction crisis. She opposed the marijuana initiative on the November ballot, citing concerns over unknown or unanswered questions about what legalization might mean to Massachusetts.

Baker also opposed the ballot question, which passed with the support of about 1.8 residents, or 56 percent of statewide voters.

A bill signed earlier this month that made revisions to the voter-approved law gave Baker, Democratic state Treasurer Deb Goldberg and Democratic Attorney General Maura Healey each a hand in appointing the Cannabis Control Commission. Goldberg is tasked with naming the person who will chair the panel. The governor’s appointee was required to have a background in public health, mental health or substance abuse.

The commission will oversee both recreational and medical marijuana. It’s charged with screening and licensing applicants for retail cannabis shops that are expected to begin opening in mid-2018.

“I look forward to serving on the commission as Massachusetts moves forward in responsibly regulating this new industry,” Flanagan said in a brief statement.

An aide said the senator planned no further comments on Wednesday.

Jim Borghesani, a spokesman for the group that led the drive to legalize recreational marijuana, said he hoped Flanagan “would put her personal position aside to advance the will of Massachusetts voters.”

He noted that Baker earlier tapped Walpole Police Chief John Charmichael Jr., an outspoken opponent of marijuana legalization, for an advisory board that will make recommendations to the regulatory commission.

As an associate commissioner, Flanagan is expected to receive an annual salary of about $120,000. She earned $84,233 as a state lawmaker in 2016, according to the state’s Open Checkbook website.

Flanagan, considered a moderate Democrat, was elected to the state House of Representatives in 2004 and to the Senate four years later.

Massachusetts is one of eight states where voters have legalized adult recreational marijuana use.